The present invention relates a small-scaled control assembly with a frusto-conical plastic sleeve arranged in a housing, and more particularly to a control assembly employed generally for a hinged structure including several personal computers with an opening and closing display unit, a stand for a portable television set, an adjustable lamp with support arms, electric goods with a lid or the like.
Laptop, palmtop or handy personal computers must be made as compact and light as possible for convenience of carrying and also must be so constituted that a small display unit with a liquid crystal panel can open and close. In order to rest the display unit at a desired position as it turns about an angle of almost 120 degree from the surface of the body, the computer is required to be provided with an assembly for controlling the turn of a pivot attached to a hinge. It is also necessary to reduce the area occupied by the control assembly as much as possible because many electronic circuit substrates are present and panel wires are complexly distributed within the personal computer.
The known control assembly used for opening and closing the display unit has a thick coil spring fastened around the hinge pivot and both ends of the coil spring are fixed to the housing. As the pivot is tightened with strong torsion of the spring, the display unit rests at a desired opening position. With relation to the known assembly, about two times the force is required to start the opening and closing motion as compared with the turning movement of the display unit, as it is impossible to control the opening and closing motion due to constant tightening of the hinge pivot with uniform strong torsion. In case the opening and closing motion of the display unit is carried out repeatedly, a contact part of the pivot with the spring is worn out and frictional resistance in the hinge increases more and more as metal grounds enter into the contact part. Consequently, the opening and closing motion of the display unit becomes difficult. Also, the cost of producing the known assembly is very expensive because the inner surface of the spring and the outer surface of the pivot are required to maintain a high accuracy to keep uniform torsion.
According to several opening and closing devices for electric goods with a lid, this applicant who applied the present invention to the Japanese Patent Office had already proposed, for example, as described in Japanese Open Publication 56-140354, 57-115345, 58-29945, 58-148165, 58-171468, 58-174463 or 58-195766. However, since the devices mentioned above are disposed vertically in any case, it is impossible substantially to dispose one of the devices inside a portable and small-scaled electronic product such as a palmtop, laptop or notebook-sized personal computer.